<!DOCTYPE html>
<html lang="zh_cn">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            width: 200px;
            height: 200px;
            border: 1px solid orange;
        }
    </style>
</head>

<body>
    <button>发送请求</button>
    <div></div>
    <script>
        const div = document.querySelector('div');
        const btn = document.querySelector('button');
        btn.onclick = function () {
            const xhr = new XMLHttpRequest();
            xhr.open('GET', 'http://127.0.0.1:8000/cors');
            xhr.send();
            xhr.onreadystatechange = function () {
                if (xhr.readyState === 4) {
                    if (xhr.status >= 200 & xhr.status < 300) {
                        div.innerHTML = xhr.response;
                    }
                }
            };
        }
    </script>
</body>

</html>